1. Field of the Invention
This invention relates generally to the field of electrical connections and more specifically to the isolation of hazardous connections in circuit board designs.
2. Discussion of the Related Art
As known in the art, the interface between a power supply and a device on a circuit board must be protected to insure that the device does not draw more power than it is able to accommodate. Protection is usually provided by fuses, coupled between the device and the power supply. In the event the device becomes overpowered, the fuse disables the conduction path between the power supply and the device, thereby protecting the device against damage.
One drawback is that the connection between the fuse and the power supply presents a safety hazard. Contact with this connection results in an unprotected draw of power directly from the power supply. The draw of power may be substantial enough to cause injury to the contacting party or to damage a contacting device.
Contact can be prevented by requiring that circuit boards having fused connections be handled using a special tool, for example when inserting or removing the board from a computer system. Using a special tool minimizes potential hand contact of a user with the board, thereby minimizing the possibility of contact with the hazardous connection. A drawback of requiring a special tool is that it increases the time required for servicing the computer system as compared to manual insertion.
Two other devices that have been used to reduce contact with hazardous connections are heat shrink tubing and fuse holders. Heat shrink tubing is applied over the fuse and then heated, causing the tubing to tightly engage the fuse and a portion of the leads. However, this has several drawbacks. First, use of heat shrink tubing is a laborious process requiring a coverage and heating step for every fuse on the board. Second, the results are often imprecise, since the coverage of each fuse will vary with typical process variations. Third, because the heat shrink tubing is extended to cover a portion of the leads of the fuse, it is often difficult to bend the leads at the appropriate angles and locations as necessary to align the leads with their destination holes in the circuit board. If the leads do not properly align with the holes in the circuit board, the fuse may not sit flush on the board. If the fuse does not sit flush on the board, an unprotected portion of the fuse may still be exposed to the user.
The second device used to isolate a hazardous connection is a fuse holder. This is a large tube fixedly coupled to enclose the fuse body and a portion of the fuse leads. However, fuse holders are expensive and require a manufacturing step to fixedly couple the fuse to the holder. In addition, the fuse holder is typically larger than the fuse itself, and thus requires an increased area for mounting on the circuit board.
Thus, it would be desirable to develop an inexpensive and reliable device for protecting a user from the potential safety hazards of fuse connections.